For liquefaction of natural gas, an LNG (liquefied natural gas: Liquefied Natural Gas) plant generally requires a pretreatment process where a liquid component (condensate) is separated from natural gas sent from a gas field, an acid gas removal process where an acid gas (hydrogen sulfide, carbon dioxide or the like) which is an environmental pollutant is removed, a process where mercury which is detrimental to a liquefaction device is removed, a dehydration process where moisture is removed by an adsorbent or the like, a liquefaction process where natural gas is liquefied in a liquefaction facility, and the like. In addition, in these gas treatment or liquefaction processes or the like, equipment, e.g., a gas compressor, is used (see, for example, Patent Literature 1: JP 2010-25152 A).
Regarding the equipment used, e.g., a compressor, in order to secure safety of the equipment, when the pressure or the like of a hydrocarbon (hydrocarbon)-containing fluid held in the equipment reaches a previously set pressure, a safety means, e.g., a safety valve and a depressurization valve, connected to the equipment is activated and is brought into a released state, so that the fluid within the equipment is released and transferred to a flare pipe which is connected in a fluid communicable manner to the safety means. In addition, the fluid sent from the flare pipe is combusted in a flare and is discharged out of the plant (liquefaction device).
FIG. 4 is a diagram schematically illustrating a conventional equipment safety management device 100. As illustrated in FIG. 4, conventionally, equipment 101 is in fluid communication with an outlet 102 of equipment and is brought into a released state when the pressure of the equipment 101 reaches a previously set pressure, and the equipment 101 is connected in a fluid communicable manner to a safety means 103 that delivers the fluid to a flare pipe 104 (first flare pipe 104), which is fluidly communicated. With this configuration, an excessive elevation of the pressure of the equipment 101, e.g., a compressor, is prevented. Additionally, in order to allow the fluid to flow from other equipment 107 via a safety means 108, a second flare pipe 105 (flare pipe 105) is disposed as a flare pipe in addition to the first flare pipe 104. The destination of connection of the safety means 103, e.g., a safety valve and a depressurization valve, is the single flare pipe 104, as illustrated in FIG. 4. It is previously determined to which flare pipe to allow the fluid within the equipment 101 to flow from the equipment 101 depending on its temperature or the degree of water content: the flare pipe 104 (first flare pipe) for flowing a fluid below the freezing point (low-temperature fluid) or the flare pipe 105 (second flare pipe) for flowing a moisture-containing fluid (aqueous fluid) (in FIG. 4, the first flare pipe 104). Based on the above, the safety means 103 and the flare pipe 104 are designed so that the operation pressure of the equipment 101 does not exceed the design pressure and the fluid is released to the flare pipe. Thus, the safety management of the equipment 101 is performed.